LET'S START WELDING

While the preceding information is important to your intelligent progress in welding ‑ we suggest you re‑read at the start of each practice session in the early stages ‑ the actual skills of laying down a weld can only be achieved by practical application. "Practice makes perfect" must also be interpreted as "Practice makes imperfect" if you are not using the correct techniques. In manual welding a number of actions must take place simultaneously, such as maintaining a correct electrode feed in, correct arc length, correct placement of metal, etc. ‑ certainly too many for continuous conscious effort by the welder over a long period. Many of these aspects will soon become a natural reflex action or habit with practice. So learn good habits, not bad habits.

Striking the Arc

(Are you wearing suitable clothing, gloves, etc., and have you checked the area for fire hazards?)

Select a piece of clean steel (say 250 x 75 x 6mm) ‑ heavy rust is a poor conductor and makes bad electrical contact ‑ and attach your work clamp to it or seat it in good contact on your welding bench. Set your machine at 120 amps and place the bared end of a 3.2mm o electrode (Austarc 12P is fine) in the holder. Turn on the welder.

If you lightly touched the end of the electrode on to work, you would complete the circuit and current would flow, the electrode end rapidly getting hot and possibly melting sufficient to momentarily weld the electrode on to the work. (No doubt you'll see what we mean before this session is finished!) On the other hand, the low voltage current we are using won't jump an air amp (as in a spark plug). We must therefore establish an arc by first touching the electrode to the work and then immediately lengthening the distance between electrode and work until the droplets of metal and slag melting from the end of the electrode can cross to the molten pool below without bridging the gap and causing a short circuit with the electrode freezing onto the work.

A simple action of striking‑an‑arc (Fig. 7) in much of the same manner as striking a match achieves this effect.

The electrode tip moves down and across, touches (a flash) and up, the arc still going until it becomes too long and extinguishes. Now, restrict your raising of the electrode tip to a maximum of 6 mm after striking the arc and endeavor to hold it steady at that point for about 10 seconds. This will necessitate feeding the electrode into the arc as the end burns off. Practice striking and holding an arc until it becomes child's play. This arc length is, of course, too long for useful welding, but will give you the feel of maintaining a length without fear of shorting. Any longer becomes unmanageable or may extinguish it, the resistance to current flow across the arc becoming too great.

If for one reason or another your action is incorrect and the electrode freezes on to the work, i.e. becomes welded to it, a sharp backward angling of the electrode should break the weld. Maintain your shield over the face until freed as it release from the plate or the electrode, will be accompanied by an arc flash.

Laying Down a Weld Bead

Once the arc has been established, reduce the arc length to about 3 mm and note that metal is beginning to mount up under the tip. Start moving the tip of the rod slowly away to the right (to the left if you are left‑handed) endeavoring to maintain a pool behind the arc approximately 6‑8mm wide. you will have to feed in the electrode at a steady rate, progress at a steady rate across the plate, maintain a steady arc length etc. Don't lose heart ‑ a little more practice and some of these actions will begin to happen automatically!

For the present, concentrate on just two things as illustrated in Fig. 8.

(i)   Maintain your arc length and as you get more experienced shorten it a little further. your other senses, like hearing, will come to your aid as you begin to recognise the sounds of the arc. By maintaining a steady and correct arc length, you must automatically be feeding the electrode in at the right speed!

(ii)    The size of your molten pool. There is a natural tendency for most beginners to travel across the plate to fast. Slow down. Angle you electrode so that it leans some 25° forward in the direction you are traveling, to tip pointing back on to the molten pool If you keep that pool at a constant width and your arc length constant you must be moving along at a steady pace. By   concentrating your attention into this one small area and on these two points ‑ arc length and weld pool size ‑ you will be learning the fundamentals of steady, even progression ‑ but you may be surprised at the snaking path you weaved in the process. Don't worry‑that aspect will fall into place as we progress with the next step. Practice!

Before leaving this section, try two more things:

1.   Aim for a bigger constant weld pool ‑ you will have to travel slower and they try for a slightly narrower bead, traveling faster. Even with the one size electrode we often use different rates of travel on different joints.

Reduce your arc length further until the electrode coating just touches the work. Easy welding if you have a suitable electrode and the right angle. As the coating burns off, the arc length and travel speed is automatically maintained. Raise the angle of the electrode and you travel slower (bigger weld), lower it and you travel faster. This touch welding technique is easy and handy, but not all electrodes are suited to it, nor is it suitable for all joints and positions. So remember it as the occasional bonus once your know how to run an electrode and can hold a steady arc and direct your metal at will.

As a general rule, the arc should be held as short as possible while still giving a stable burn off and good weld appearance. Too long an arc gives an unwieldy flow of metal with rough weld appearance and reduced penetration. Too short an arc gives a high narrow bead and a stutter characteristic with the electrode liable to freeze on to the work.

Building a Pad

For economical use of your steel and all‑round practice at the principle of achieving a straight even weld bead, there is not better practice than laying down a solid pad of weld metal. Take a fresh piece of steel (say 200 x 75 x 1 Omm) and mark two lines down the centre of the length of plate approx. 6mm apart with chalk or regular pop marks.